[Embargoed for release
until 2:35 p.m. ET, Monday, August 23, 2004, to coincide with presentation
at the American
Chemical Society meeting in Philadelphia.]

PAINT ABSORBS CORROSION-CAUSING CHEMICALS, KITTY-LITTER STYLE

PHILADELPHIA – Engineers at Ohio State University have incorporated
clay and other chemicals into a paint that keeps metal from corroding
-- and reveals when an airplane, boat, or bridge needs to be repainted.

Though the paint is still under development, early tests have shown that
it prevents corrosion just as well as commercial paints that are less
environmentally friendly.

Rudolph
Buchheit

Santi
Chrisanti

The new paint is unique because its pigment contains tiny particles
of clay that capture the chemicals that cause corrosion. It also releases
just the right amount of a corrosion-fighting agent when needed, explained
Rudolph
Buchheit, professor of materials
science and engineering.

“It works kind of like high-tech kitty litter,” he said.

With further development, the pigment could enable maintenance crews
to inspect surfaces using a common X-ray technique to determine when they
need to be repainted.

Buchheit and doctoral student Santi Chrisanti described the project
Monday, August 23, at the meeting of the American Chemical Society in
Philadelphia.

The pigment contains cerium, one of several natural anti-corrosion minerals
known as rare earth elements. Coatings inside self-cleaning ovens often
contain cerium, but those coatings are passive -- they release cerium
continually until the element is gone. Scientists have been working for
years to create “smart pigments” that can do more.

“The challenge has been how to keep these rare earth elements
stored in a paint and then release them on demand, just when conditions
are right for corrosion,” Buchheit said.

“Real corrosion-resistant
paints are highly engineered,” he said. “They’ve
been given all kinds of additives to make them flow better or to
give them a fine gloss -- things we haven’t yet worried about.”

Chloride is the chemical responsible for most metal corrosion. Water
is another key ingredient, and water that contains salt, or sodium chloride,
is particularly corrosive. When paint cracks or wears off, a chemical
reaction with the chloride eats away the exposed metal -- a serious problem
for critical structures on vehicles or bridges.

To fight corrosion, the new pigment absorbs chloride, and releases cerium
or other corrosion inhibitors to form a protective film over cracks in
the paint.

In tests, the engineers coated pieces of metal with the new paint formulation,
and scratched the surface to simulate severe paint wear. Then they subjected
the metal to a constant saltwater fog in a laboratory corrosion chamber.

After 1,000 hours, the metal remained corrosion-free -- a performance
comparable to commercial paints.

But those commercial paints prevent corrosion using chromate -- a toxic
chemical that rose to public awareness with the release of the film Erin
Brockovich. Chromate must be carefully disposed of, to keep it from
entering the water supply.

And if cerium or other another corrosion inhibitor were to enter the
water supply? Buchheit admits that is a question better left to toxicologists
than materials scientists, but to his knowledge the chemicals he is studying
do not appear to pose the same health hazards.

In another result of their laboratory tests, the engineers confirmed
that a technique called X-ray diffraction can be used to measure how much
cerium was released to fill the cracks, and how much was left in the paint
-- an indicator of whether a piece of metal would need to be repainted.

With this technique, X-rays bounce off of the crystalline clay additives
to form a pattern. Because the pattern is unique to every material, scientists
can use X-ray diffraction to read a substance’s chemical fingerprint.

Buchheit pointed out that the use of a different X-ray technique, X-ray
radiography, is now routine for studying airplanes, bridges and boats:
“We want to make our replacement technology as much like the incumbent
technology as we can, so people can use the same expertise and equipment
to get the job done. X-ray diffraction is not as common outside of the
research laboratory as X-ray radiography, but it’s not unprecedented,
either.”

He envisions that maintenance crews would set up an X-ray diffraction
machine on a rack that rolled over an object, such as an airplane wing.
The process could be automated.

The engineers continue to work on the pigment, which should work with
just about any corrosion inhibitor, not just cerium. Other possibilities
that Buchheit’s team are currently studying include molybdenum and
vanadium.

Buchheit emphasized, however, that the new pigment is far from a commercial
product.

“Real corrosion-resistant paints are highly engineered,”
he said. “They’ve been given all kinds of additives to make
them flow better or to give them a fine gloss -- things we haven’t
yet worried about.”